antipaucity

fighting the lack of good ideas

4 places to check your website’s ssl/tls security settings

Qualys – https://www.ssllabs.com/ssltest

High-Tech Bridge – https://www.htbridge.com/ssl

Comodo – https://sslanalyzer.comodoca.com

SSL Checker – https://www.sslchecker.com/sslchecker

update: keeping your let’s encrypt certs up-to-date

Last year I posted a simple script for keeping your Let’s Encrypt SSL certificates current.

In conjunction with my last post sharing the “best” SSL configs you can use with Apache on CentOS, here is the current state of the cron’d renewal script I use.

systemctl stop httpd.service
systemctl stop postfix
~/letsencrypt/letsencrypt-auto -t -n --agree-tos --keep --expand --standalone certonly --rsa-key-size 4096 -m user@domain.tld -d domain.tld
# you can append more [sub]domains to a single cert with additional `-d` directives ([-d otherdomain.tld [-d sub.domain.tld...]])
#...repeat for every domain / domain group
systemctl start httpd.service
systemctl start postfix

I have this script running @weekly in cron. You should be able to get away with doing it only every month or two .. but I like to err on the side of caution.

I’m stopping and starting Postfix in addition to httpd (Apache on my system) for only two reasons: first, I am using some of the LE-issued certs in conjunction with my Postfix install; second, because I don’t know if Dovecot and my webmail system need to make sure Postfix is restarted if underlying certs change.

ssl configuration for apache 2.4 on centos 7 with let’s encrypt

In follow-up to previous posts I’ve had about SSL (specifically with Let’s Encrypt), here is the set of SSL configurations I use with all my sites. These, if used correctly, should score you an “A+” with no warnings from ssllabs.com. Note: I have an improved entropy package installed (twuewand). This is adapted from the Mozilla config generator with specific options added for individual sites and/or to match Let’s Encrypt’s recommendations.

Please note: you will need to modify the config files to represent your own domains, if you choose to use these as models.

[/etc/httpd/conf.d/defaults.conf]

#SSL options for all sites
Listen 443
SSLPassPhraseDialog  builtin
SSLSessionCache         shmcb:/var/cache/mod_ssl/scache(512000)
SSLSessionCacheTimeout  300
Mutex sysvsem default
SSLRandomSeed startup builtin
SSLRandomSeed startup file:/dev/urandom  1024
# requires twuewand to be installed
SSLRandomSeed startup exec:/bin/twuewand 64
SSLRandomSeed connect builtin
SSLRandomSeed connect file:/dev/urandom 1024
SSLCryptoDevice builtin
# the SSLSessionTickets directive should work - but on Apache 2.4.6-45, it does not
#SSLSessionTickets       off
SSLCompression          off
SSLHonorCipherOrder	on
# there may be an unusual use case for enabling TLS v1.1 or 1 - but I don't know what that would be
SSLProtocol all -SSLv2 -SSLv3 -TLSv1 -TLSv1.1
SSLCipherSuite ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256
SSLOptions +StrictRequire
SSLUseStapling on
SSLStaplingResponderTimeout 5
SSLStaplingReturnResponderErrors off
SSLStaplingCache        shmcb:/var/run/ocsp(128000)

#all unknown requests get domain.tld (over http)
<VirtualHost *:80>
    DocumentRoot /var/html
    ServerName domain.tld
    ServerAlias domain.tld *.domain.tld
    ErrorLog logs/domain-error_log
    CustomLog logs/domain-access_log combined
    ServerAdmin user@domain.tld
    <Directory "/var/html">
         Options All +Indexes +FollowSymLinks
         AllowOverride All
         Order allow,deny
         Allow from all
    </Directory>
</VirtualHost>

SetOutputFilter DEFLATE
AddOutputFilterByType DEFLATE text/html text/plain text/xml text/javascript text/css text/php

[/etc/httpd/conf.d/z-[sub-]domain-tld.conf]

<Virtualhost *:80>
    ServerName domain.tld
# could use * instead of www if you don't use subdomains for anything special/separate
    ServerAlias domain.tld www.domain.tld
    Redirect permanent / https://domain.tld/
</VirtualHost>

<VirtualHost *:443>
    SSLCertificateFile /etc/letsencrypt/live/domain.tld/cert.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/domain.tld/privkey.pem
# if you put "fullchain.pem" here, you will get an error from ssllabs
    SSLCertificateChainFile /etc/letsencrypt/live/domain.tld/chain.pem
    DocumentRoot /var/www/domain
    ServerName domain.tld
    ErrorLog logs/domain-error_log
    CustomLog logs/domain-access_log \
          "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
    ServerAdmin user@domain.tld

# could put this in defaults.conf - I prefer it in each site config
    SSLEngine on

<Files ~ "\.(cgi|shtml|phtml|php3?)$">
    SSLOptions +StdEnvVars
</files>
<Directory "/var/www/cgi-bin">
    SSLOptions +StdEnvVars
</Directory>

SetEnvIf User-Agent ".*MSIE.*" \
         nokeepalive ssl-unclean-shutdown \
         downgrade-1.0 force-response-1.0

    <Directory "/var/www/domain">
         Options All +Indexes +FollowSymLinks
         AllowOverride All
         Order allow,deny
         Allow from all
    </Directory>

</VirtualHost>

I use the z....conf formatting to ensure all site-specific configs are loaded after everything else. That conveniently breaks every site into its own config file, too.

The config file for a non-https site is much simpler:

<VirtualHost *:80>
    DocumentRoot /var/www/domain
    ServerName domain.tld
    ServerAlias domain.tld *.domain.tld
    ErrorLog logs/domain-error_log
    CustomLog logs/domain-access_log combined
    ServerAdmin user@domain.tld
    <Directory "/var/www/domain">
         Options All +Indexes +FollowSymLinks
         AllowOverride All
         Order allow,deny
         Allow from all
    </Directory>
</VirtualHost>

If you’re running something like Nextcloud, you may want to turn on Header always set Strict-Transport-Security "max-age=15552000; includeSubDomains" in the <VirtualHost&gt directive for the site. I haven’t decided yet if I should put this in every SSL-enabled site’s configs or not.

putting owncloud 8 on a subdomain instead of a subdirectory on centos 7

After moving to a new server, I wanted to finally get ownCloud up and running (over SSL, of course) on it.

And I like subdomains for different services, so I wanted to put it at sub.domain.tld. This turns out to be not as straight-forward as one might otherwise hope, sadly – ownCloud expects to be installed to domain.tld/owncloud (and plops itself into /var/www/owncloud by default (or sometimes /var/www/html/owncloud).

My server is running CentOS 7, Apache 2.4, and MariaDB (a drop-in replacement for MySQL). This overview is going to presume you’re running the same configuration – feel free to spin one up quickly at Digital Ocean to try this yourself.

Start with the ownCloud installation instructions, which will point you to the openSUSE build service page, where you’ll follow the steps to add the ownCloud community repo to your yum repo list, and install ownCloud. (In my last how-to, 8.0 was current – 8.2 rolled-out since I installed 8.1 a couple days ago.)

Here is where you need to go “off the reservation” to get it ready to actually install.

Add a VirtualHost directive to redirect http://sub.domain.tld to https://sub.domain.tld (cipher suite list compiled thusly):


<VirtualHost *:80>
ServerName sub.domain.tld
Redirect permanent / https://sub.domain.tld/
</VirtualHost>

Configure an SSL VirtualHost directive to listen for sub.domain.tld:


<VirtualHost *:443>
SSLCertificateFile /etc/letsencrypt/live/sub.domain.tld/cert.pem
SSLCertificateKeyFile /etc/letsencrypt/live/sub.domain.tld/privkey.pem
SSLCertificateChainFile /etc/letsencrypt/live/sub.domain.tld/fullchain.pem
DocumentRoot /var/www/subdomain
ServerName sub.domain.tld
ErrorLog logs/subdomain-error_log
CustomLog logs/subdomain-access_log "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
ServerAdmin user@domain.tld
SSLEngine on
SSLProtocol all -SSLv2 -SSLv3
SSLCipherSuite ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256
SSLHonorCipherOrder on
SSLOptions +StdEnvVars
<Directory "/var/www/cgi-bin">
SSLOptions +StdEnvVars
SetEnvIf User-Agent ".*MSIE.*" nokeepalive ssl-unclean-shutdown downgrade-1.0 force-response-1.0
# allow .htaccess to change things
<Directory "/var/www/subdomain">
Options All +Indexes +FollowSymLinks
AllowOverride All
Order allow,deny
Allow from all
</Directory>
</VirtualHost>

Comment-out every line in (or remove) /etc/httpd/conf.d/owncloud.conf.

Move /var/www/html/owncloud/* to /var/www/subdomain.

Make sure permissions are correct on /var/www/subdomain:

  • chown -R :apache /var/www/subdomain

Run the command-line installer: /var/www/subdomain/occ maintenance:install

Fix ownership of the config file, /var/www/subdomain/config/config.php to root:apache.

In config.php,

  • change trusted domains from ‘localhost‘ to ‘sub.domain.tld
  • make sure ‘datadirectory‘ is equal to /var/www/subdomain/data
  • change ‘overwrite.cli.url‘ from ‘localhost‘ to ‘https://sub.domain.tld

Navigate to http://sub.domain.tld, and follow the prompts – and you should be a happy camper.

automated let’s encrypt ssl certificate renewal on centos 7

In my how-to for Let’s Encrypt, I gave an example script that can be called via cron (or manually) which will renew Let’s Encrypt SSL certificates under CentOS 6.

If you want to do it on CentOS 7 (which is what I am now running), use the following:

cd ~/letsencrypt
git pull
systemctl stop httpd.service
~/letsencrypt/letsencrypt-auto --agree-tos --keep --rsa-key-size 2048 --standalone certonly -m user@domain.tld -d domain.tld [-d sub.domain.tld [-d ...]]
systemctl start httpd.service

Now, what does this script do? Step by step:

  1. clear-out the last grab of the Let’s Encrypt git repo (there’s probably a better way to do this, but I don’t know what it is)
  2. go to root’s home (/root)
  3. clone-down the Let’s Encrypt toolset
  4. stop httpd (Apache in my case, though you might be running nginx or something else
  5. run the cert tool in automated form:
    1. agree to terms of service
    2. keep current cert if it doesn’t need to be updated
    3. key size of 2048 bits
    4. run the standalone webserver to verify “ownership” of the domain
    5. generate just the cert
    6. administrative email (optional, but “encouraged”)
    7. domain(s) to issue cert for (must be individually identified with successive -d flags; LE does not support wildcard certs)
  6. restart httpd

I set mine to run @weekly in cron@monthly is likely good enough, but since it’s “free” to run, running slightly more than is necessary seems good to me. Plus, if you’re getting SSL certs for many domains all being served from the same server, they may have different expiration dates, so running more often is better.

My crontab entry for renewing certs:

@weekly /root/renew-le-ssl.sh

dave winer is wrong

Or maybe he’s right. But for the wrong reason.

Over on Medium, which is where I saw his post, Dave said:

“The problem of requiring HTTPs in less than 140 chars: 1.Few benefits for blog-like sites, and 2. The costs are prohibitive.

There’s actually a #3 (sorry) — 3. For sites where the owner is gone the costs are more than prohibitive. There’s no one to do the work.”

While this was more-or-less true-ish in times gone by, with the advent of truly-free SSL (and not merely the manual free edition you could get from StartSSL) from Let’s Encrypt (see my how-to), automated, hands-off maintenance of your SSL-iness is possible (and encouraged).

There are, potentially, good reasons for saying SSL won’t be required. But blaming costs, upkeep, and “few benefits” are not among them. If anything, SSL-ifying your blog will help with some (not all) attacks launched against self-hosted/-managed services where login data can be otherwise captured in plaintext.

Dave, I like you. But you’re wrong on this one.

let’s encrypt centos 6 – truly free ssl

There’s been quite a bit of excitement surrounding Let’s Encrypt recently – a truly 100% free SSL issuer.

Last week I helped a friend of mine get his first Let’s Encrypt certificate generated and configured for his website. One of the things I found incredibly frustrating is that Let’s Encrypt does not have a package for Red Hat/CentOS/Fedora! Ignoring such a massive installed base seems monumentally dumb – so I hope that they correct it soon. Until they do, however, here’s a tutorial that should cover the gotchas for getting Let’s Encrypt to work on a CentOS 6 server with Apache 2.

The documentation (as of 06 Jan 2015) on the Let’s Encrypt website is in error in a few places (or, at least, not as correct as is could/should be). One big thing to note, for example, is that it says Python 2.6 is supported (the current release for RHEL/CentOS 6). If you run the certificate generator without the --debug flag, though, it will error-out saying Python 2.6 is not supported.

While I used an existing CentOS 6 server, I’ll start this tutorial as I have many others – by telling you to go get a CentOS 6 server from Digital Ocean or Chunk Host.

Preliminaries

Login as root (or a sudo-privileged account – but root is easier), and install Apache, Python, and SSLyum install httpd python mod_ssl.

Also enable the EPEL repository: yum install epel-repository (available from the CentOS Extras repository. I’m going to assume you are familiar with configuring Apache, and will only provide the relevant snippets from ssl.conf herein.

Now that the basics are done, let’s move to Let’s Encrypt. I ran the tool in interactive mode (which is going to require ncurses to be available – it’s probably already installed on your system) – but you’ll want to add a crontab entry since Let’s Encrypt certs expire after 90 days, so I’ll compact the interactive session into a single command-line call at the end, which you’ll need to “know” how to do, since the --help argument doesn’t do anything yet (that I could find).

Initial Certificate Creation

First, grab the latest Let’s Encrypt from GitHub:
git clone https://github.com/letsencrypt/letsencrypt && cd letsencrypt

Stop Apache: service httpd stop. Let’s Encrypt is going to try to bind to ports 80 and 443 to ensure you have control the domain.

Now run the letsencrypt-auto tool – in debug mode so it’ll work with Python 2.6: ./letsencrypt-auto --debug certonly.

Use certonly because the plugins to automate installing for Apache and Nginx don’t work on CentOS yet.

Enter your domain name(s) for which you want to issue a certificate. If you accept incoming connections to www.domain.tld and domain.tld, be sure to put both in the list (likewise, if you have, say, blog.domain.tld that you want included).

Enter an administrative email address.

When the tool finishes, it’ll put symlinks in /etc/letsencrypt/live/domain.tld, with the “actual” certs in /etc/letsencrypt/archive/domain.tld. We’re going to reference the symlinks in /etc/letsencrypt/live/domain.tld next.

Edit /etc/httpd/conf.d/ssl.conf (I prefer emacs – but use whatever you prefer), and add the following lines in your VirtualHost directive:
SSLCertificateFile /etc/letsencrypt/live/domain.tld/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/domain.tld/privkey.pem
SSLCACertificateFile /etc/letsencrypt/live/domain.tld/cert.pem

Restart Apacheservice httpd start.

Try hitting https://domain.tld in your web browser – and you should be golden!

Automating Renewal

Create a small shell script called renew-LE-certs.sh somewhere you’ll remember where it is – like /root:
service httpd stop
# add additional '-d' entries for more subdomains
/path/to/letsencrypt/letsencrypt-auto --debug --keep --agree-tos --rsa-key-size 2048 certonly -m ssladmin@domain.tld -d domain.tld -d www.domain.tld
service httpd start

For your crontab entry, do the following to setup monthly cert renewal:
@monthly /path/to/renew-LE-certs.sh